The tolerance limit of Aspergillus niger NRRL 322 for the heavy metals like, Cd, Pb, Cr and Mo is analyzed as a part of the batch fermentation study undertaken. Computation of the kinetic parameters like, growth rate ( ), specific growth rate (max), the saturation constant for the limiting nutrient (Ks), the growth yield (K), the growth lag (L) and the lag time (Tl) are done and correlated with the microbial metabolism. A detailed study on the growth rate of Aspergillus niger with glucose as the substrate in the presence of transition metals is done and the subsequent excretion of metabolic products associated with the growth in a batch fermentation are discussed. Hitherto reports document the growth yield of a microbe to be constant only with organic sources, but surprisingly, the growth yield of the strain is observed to be constant with an inorganic source like, Cd. Among the metal ions tried for batch fermentation, trial order of growth yield is found to be Mo > Cr > Pb > Cd and the biosynthesis of citric acid is more with Cd as a stimulant.

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